Old Rocks
Diamond Member
At approximately 12 km/h rolling and air resistance have equivalent magnitude. At higher velocities air resistance dominates quite strongly.
That is for bicycles. While a bicycle has more resistance (Cd) than a car, the curve is about the same.
Aerodynamic Drag - The Physics Hypertextbook
In some situations, however, this may not be entirely correct. Drag is a complex phenomena. It cannot always be described with equations that are simple. My first guess would always be that drag is proportional to the square of speed since I understand and like the derviation I've presented, but I would not be surprised if (over some range of values) drag and speed were found to be directly proportional, proportional to some power besides 2, or related by some polynomial. Welcome to the world of empirical modeling — where relationships are determined by actual physical experiments rather than an ideology of pure theory. More on this subject later in this section.
That is for bicycles. While a bicycle has more resistance (Cd) than a car, the curve is about the same.
Aerodynamic Drag - The Physics Hypertextbook
In some situations, however, this may not be entirely correct. Drag is a complex phenomena. It cannot always be described with equations that are simple. My first guess would always be that drag is proportional to the square of speed since I understand and like the derviation I've presented, but I would not be surprised if (over some range of values) drag and speed were found to be directly proportional, proportional to some power besides 2, or related by some polynomial. Welcome to the world of empirical modeling — where relationships are determined by actual physical experiments rather than an ideology of pure theory. More on this subject later in this section.